In general, a rotary mount comprises two rings that can be rotated relative to each other, each ring having a raceway, and the mount further comprises bearing means constituted by rolling bodies or members (such as balls or wheels) interposed between the two raceways, and a device for holding together the elements making up the mount and for preventing it coming apart, while allowing the two rings to rotate relative to each other.
Blow-molding machines usually include such a rotary mount. Such blow-molding machines are conventionally provided with a plurality of mold units carried by a carousel which is rotatable about an axis that is substantially vertical. For this purpose, one of the rings is connected to the frame of the machine, and the carousel is carried by the other ring. Thus, the carousel can rotate relative to the frame. The ring connected to the frame is said to be the stationary ring, and the other ring is said to be the rotary ring. The rotary ring, and thus the carousel, is rotated by a motor, generally not directly, but via gear and/or belt mechanisms.
The Applicant has found that relatively modest and localized heating of the mount in a blow-molding machine occurs during ordinary use of such machines.
For a mount having a diameter of 1800 millimeters (mm) and rotating at 30 revolutions per minute (rpm), the rotating mass being 18 metric tonnes (T), the Applicant has observed localized heating of about 25° C.
That phenomenon has remained unnoticed until now, doubtless in part because the rotary mount is located in the core of a machine that is very compact, said machine having very many members moving at high speed when the machine is in operation.
The phenomenon has doubtless also remained unobserved because it is of very small amplitude, localized heating of about 25° C. being very likely to pass unnoticed in the core of a machine having numerous members that are dissipating heat, particularly in an industrial environment.
The Applicant suggests that such localized and modest heating of the rotary mount might nevertheless lead to significant consequences, such localized heating causing the mount to expand very slightly, which can lead to small variations in operating clearances, and to premature wear of certain parts.
On the basis of this discovery of localized and modest heating, and assuming that there exists correlation between said modest rise in temperature and certain variations in the operating clearances of the machine, the Applicant has set out to mitigate this apparent technical problem.
The Applicant has thus devised means enabling said localized heating to be controlled, in order to reduce it or even eliminate it, so as to reduce undesirable phenomena such as operating clearances appearing in the vicinity of certain machine parts, with such means being suitable for putting into place on existing machines. Initially, several approaches did not give satisfaction.
A first approach consisted in providing the moving ring with fins. A second approach consisted in using air to spray oil onto the bearing device: that approach turned out to be incompatible with machines for blow-molding receptacles since it led to unwanted pollution of the machine, which pollution could reach the receptacles, which is unacceptable.